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plugnplay 0.5.0

Plug n’ Play

Plug n’ PLay (PnP) is a Generic plug-in system inspired by Trac’s (http://trac.edgewall.org)
internal component management. With PnP you can turn any program into a pluggable software very easily.

You just have to define the Interfaces and let others implement them. When your code is running
you can dynamically retrieve who are the classes that implement a certain Interface, and call
the specific methods.

A simple example

Think this way: You have e very simple program that just copy files around.

Say you want to check if the copy was OK by calculating the MD5 hash of the
two files (the original and the copy). You can do this implementing the MD5 check
inside your main code, that’s OK too, but when you need to add another check
(e.g. calculate the SHA-1 of the files) you will have to modify your code so
it can call two methods, the MD5 checker and the SHA-1 checker.

With PnP you write only the main piece of the program, the part that does only the copying,
and the hash checkers you can implement whenever you want, without any modification
to the main code.

New in version 0.5.0

Features

MyInterface.implementors() now can receive a callback function and any number of arguments or keyword arguments. This callback will be called for each implementor, only implementors for which callback(implementor) returns True will be included on the resulting filtered list. Any extra arguments passed to MyInterface.implementors() will be passed through to the callback function. Here is a Simple example:

In this case, both filtered_implementors and filtered_implementors_1 will be the same: It will be a list containing an instance of ImplementorOne. Since the example callback has a keyword argument we can also call MyInterface.implementors(_filter_implementors) and you will have a list returned with an instance of ImplementorFour.

Fixes

Fixed issue #5: Now all plugins are loaded in alphabetical order. The sorting is made among all plugin filenames in all plugin dirs that were added with set_plugin_dirs() function. As an example, consider this plugindirs structure:

Assuming you added your plugin folders in this order: myplugins, myplugins/dir1 and myplugins/dir2, your plugins will be loaded in this order: aplug.py, dir1/aplug.py, dir2/bplug.by, dir1/cplug.py, dir2/dplug.py, dir2/pplug.py, zplug.py. Not that this does not dictates the order of execution of the implementors of a given interface (when you call MyInterface.implementors()).

Fix issue #13. Plugnplay should create instances only of classes which implements at least one plugnplay.Interface.

New in version 0.4.2

Small fix when installing plugnplay. The README.rst file was not being included in th final sdist package.

New in version 0.4

Since plugnplay version 0.4 you can call your Interface method directly, like this:

CopyListener.copy_finished(file1, file2)

This line will call the copy_finished method of all objects that implement the CopyListener interface.
This is speciallt iseful when you just want to call all listeners, but do not have any interest on their return value.

Conclusion

Did you like this project? Very nice, so help me write it! Fork the repo and
send me some pull requests! Or talk to me directly if you have some great ideas to implement!